Water purification devices which purify at slow rate, such as those which use the distillation and the reverse-osmosis processes, deliver water into a storage tank or reservoir from which the water is dispensed. The same is true in regard to systems which use bottled water and water filter dispensing coolers. The water, however, may be easily contaminated with bacteria by contact with air on the storage and dispensing mechanisms, or merely by sitting stagnant in the reservoir. This is particularly true with bottled water cooler dispensers and those units that are used as replacements for bottled water cooler dispensers since the tanks are non-pressurized, and therefore must be vented to permit water to be dispensed by gravity flow.
A known method for eliminating bacterial contamination is the use of ultra-violet (xe2x80x9cUVxe2x80x9d) light. The light energy from a UV lamp is germicidal, because UV light penetrates microbial organism""s protective membrane layer and photochemically damages the DNA structure, disabling its self-reproducing capability and rendering the cell lifeless.
UV light is in the region of the electromagnetic spectrum that lies between visible light and X-rays. The ultra-violet spectrum ranges from 100 nm to 400 nm wave lengths, with the optimum effective range between 250 nm to 270 nm. The UV lamp is commonly housed in a protective sleeve of quartz which is similar to a test tube that allows ultraviolet transmission and separates the lamp and wiring from the water surrounding the lamp. The quartz sleeve also helps the UV lamp to maintain its optimal operating temperature of approximately 105xc2x0 F. Factors that determine a UV system""s effectiveness include the intensity of the lamp, the exposure time of the water to the ultra-violet rays and the water transmission rate which is determined by the quality and color of the water.
The typical storage reservoir for water purification units is not usually suitable for effective UV application. In gravity-filled storage reservoirs, there must be a method for controlling the water level within the reservoir, and typically a float valve or switch is used. With a UV bulb inside the reservoir, a float valve or switch would normally act as an obstruction to the UV light rays, and provide a sheltered location for bacterial contamination to grow. A typical size and storage capacity for a point of use reservoir is in the order of approximately 4 to 6 gallons, which is required to compensate for the slow recovery rate of the purification system. Since UV has a limited effective transmission distance, the physical dimensions of a 4 to 6 gallon storage reservoir have not been suitable for effective UV application. A very high intensity UV lamp would be required in such cases and this would heat the chilled water thereby reducing the efficiency and effectiveness of the chilling process. Moreover, UV degrades most plastics, and typically in large reservoirs, floats and switches are constructed of plastic. A typical point of use and bottled water dispenser reservoir is divided into two compartments by an internal baffle that separates the water which has been cooled from the water that is still at room temperature. Two faucets are used, one for dispensing room temperature water and the other for dispensing chilled water. The baffle that separates the cold and room temperature sections blocks UV rays from reaching one of the compartments in such systems.
It has been observed in U.S. Pat. No. 6,139,726 that the known prior art has not solved any of these problems. Although U.S. Pat. No. 6,139,726 is a large improvement over the prior art, there still remains a need to reduce the cycling on and off of the UV bulb as well as the xe2x80x9conxe2x80x9d time of the bulb as these factors degrade the life of the bulb. Additionally, since the UV lamp is most effective at an optimal operating temperature, it would be advantageous to have the UV lamp at the optimal operating temperature before admitting water into the tank. Furthermore, if the water supply to the tank fails, there is no system in place to de-activate the UV lamp which would otherwise stay energized heating the water in the tank thereby increasing the power requirements until the bulb bums out. Another need exists for the water in the tank to be treated periodically, even when the water has not been dispensed over a period of time. Finally, as the UV lamp ages, its output decreases. Accordingly, a need exists to increase exposure of the UV lamp to the water as the lamp ages.
Consequently, it is a primary object of the present invention to provide a water dispensing system for dispensing room temperature and chilled water which has been treated and purified by an ultraviolet source.
It is another object of the present invention to provide a water treatment tank having an ultraviolet energy source therein for effectively decontaminating both room temperature and chilled water which may be contained therein, the tank receiving water from a clean water source such as a distillation/condensation purifier, a point of use filtration source, a reverse osmosis purifier or a bottled water source.
It is a further object of the present invention to provide a water dispensing system including a treatment tank having an ultraviolet (UV) energy source in the form of a lamp for purifying the water therein, the water entering the tank after the UV lamp reaches the optimal operating temperature.
It is a still further object of the present invention to provide a water dispensing system including the treatment tank having an ultraviolet (UV) energy source in the form of a lamp for purifying the water therein, the water being exposed to UV rays while being added to the tank and periodically when not dispensing water from the tank.
It is a yet still further object of the present invention to provide a water dispensing system including a treatment tank having an ultraviolet (UV) energy source in the form of a lamp for purifying the water therein, the lamp being activated for longer periods of time over the life of the lamp.
It is a still further object of the present invention to provide a water dispensing system including a treatment tank having an ultra-violet energy source in the form of a lamp for purifying the water therein, a supply of water being located between a high and a flow limit switch.
Another object of the present invention is to determine whether or not the water supply has failed, and if so, to shut the fill valve and secure the UV lamp.
Accordingly, the present invention provides a water dispensing system wherein the water is treated by ultraviolet rays in a treatment tank to purify the water prior to being dispensed. Water entering into the treatment tank is directed so that it is channeled onto the UV lamp where it flows about the sleeve of the lamp in a thin film greatly increasing the ultraviolet exposure so that a low energy lamp may be effective even under full flow conditions. The treatment tank may have separating baffle which separates room temperature water from chilled water and the ultraviolet lamp extends into both compartments. Moreover, a transparent tube preferably formed from polytetrafluorethylene (e.g. Teflon) or the like extends through the chilled water compartment below the baffle and communicates the room temperature water with the outlet faucet therefor. The water in the tube is thus radiated by the ultraviolet light emanating from the bulb while the room temperature water is within the tube waiting to be dispensed.
A controller coordinates the operation of the UV lamp with the operation of a solenoid valve so that the lamp may be cycled on and then off to reduce the amount of heat generated within the tank. Furthermore, the controller may allow for the lamp to reach an optimal operating temperature before allowing the solenoid valve to be opened. A low and a high water level limit switch are provided within the tank so that when the water reaches the low level limit, a signal is sent to the controller to initiate filling the tank, and thus opening the valve. When the water level reaches the high water level limit, the controller sends a signal to shut the solenoid valve. If the high level limit is not reached in a predetermined time period, the fill valve may be secured for a first period of time and The process repeated after a second period of time. When the valve is secured between the first and second period of time, the lamp may be turned off. By spacing the high and low level limits a set volume of water apart, the cycling of the fill valve may be reduced which will extend the life of the lamp which treats the water as it enters the tank. Also, after a predetermined period of time of low, or non-use, the UV lamp may be cycled on and off to prevent growth within the tank. Finally, as the UV lamp ages, the period of time the lamp remains on may be increased by the controller.